1. Field of the Invention
The present invention relates to a variable valve-actuating mechanism for an internal combustion engine, and to an engine incorporating the valve-actuating mechanism. More particularly, the present invention relates to a variable valve-actuating mechanism including an unlocking mechanism, integrally assembled in a retention member, for selectively releasing a locking structure for a rocker arm, and to an internal combustion engine incorporating the described valve -actuating mechanism.
2. Description of the Background Art
One known variable valve-actuating mechanism includes a rocker arm, disposed between an engine valve and a corresponding cam on an intake-side or an exhaust-side of an internal combustion engine, and first and second cams relative to the engine valve. A rocker arm shaft which pivotally supports the rocker arm is axially movable along an axial direction thereof, with the rocker arm axially sliding along with the rocker arm shaft according to the axial movement thereof, thereby allowing the rocker arm to selectively engage either a first cam or a second cam to change operation of the engine valve (see, for example, Japanese Utility Model Laid-open No. Sho 62-711 (JP '711)). The known mechanism further includes a release member which, in order to let the rocker arm slide in time with a rotation timing of a camshaft, unlocks a lock mechanism for temporarily holding the rocker arm in place, in time with a predetermined rotation timing of the camshaft.
In the variable valve-actuating member of JP '711 as described above, the release member is inserted in a retention member in a journal bearing, and is capable of making a reciprocating motion by having an end portion in a sliding contact with a cam surface of the camshaft. The release member is, however, held in position simply by being clamped between the retention member and the camshaft, and has no fixing structure relative to the retention member.
When such a known subassembly, including the release member inserted in the retention member, is to be mounted on the camshaft, the release member can fairly easily slip out of position. Thus, such a subassembly may not always be adequately assembled to an engine main body, or extra assembly time, effort and expense may be required to manually re-insert the release member into the retention member, in instances where it has slipped out of position.
The present invention has been made to overcome such drawbacks of the existing variable valve-actuating mechanism. Accordingly, it is one of the objects of the present invention to provide a variable valve-actuating mechanism having an unlocking mechanism which is integrally assembled with a retention member, in which structure is provided to enable improved retention of the release member in the retention member, thereby achieving a more efficient assembly process.